That is one video I will remember. That river looks very similar to Smokies streams. It makes you think that maybe in our lifetime the streams in the Smokies will look like that. Just a horrible thing to watch.

The gunpowder is a tail water, much like ours here in east tn. Just like the gunpowder our tailwaters have didymo, and somehow the mountains year after year stay clear of it. I believe the video did say that extremely high flows help to scouge the bottom clean of the didymo, so maybe our 2 or 3 mini floods a year in the mountains helps actually keep the rivers from getting it? I also wonder hour didymo affects spawning? Surely it cannot help. With that said, I will keep wearing my felt soles. I dry them completely, and do not hop from tailwaters to the mountains in one day. I also believe that it is useless to ban felt when our fly line, flies, gloves, pants, anything neoprene, birds, and who knows what else transports as much if not more micro organisms than our felts soles do.

That is a good point 2weight I have never seen a mountain stream anywhere with Didymo that I noticed. I wonder if it just isn't possible due to the high flows or maybe would only be possible in the lower reaches of places like Abrams or the Little River. I have seen the slime on the rocks through Townsend and wondered if that was Didymo.

I seem to recall reading somewhere that either the wider variation in water temps or the comparatively lower amount of direct sunlight on mountain streams vs tailwaters is believed to account for why didymo is not generally found in the mountains. I'll have to see if I can find where I read that and post a link.

Also, FWIW, I think I recently ran across a report that said recent research in New Zealand(?) showed improved populations of scud and other small aquatic critters in the didymo infested rivers that might actually lead to improved trout food sources in those rivers. Therefore didymo might not be the harbinger of doom that folks have been worried that it would be. Certainly something that may deserve more research.

OK, here's some info from research done in New Zealand that helps explain why didymo is more of a problem in tailwaters and large western rivers than in the freestone mountain streams in this area. (Warning - Large PDF file > 1mb) http://www.biosecurity.govt.nz/files...nts-sep-05.pdf

According to the table on page 16, didymo fares best in water ranging in temp between 6 - 20 degrees Celsius (42 - 68 degrees Farenheit). Score one for tailwaters. Freestones generally have wider variation.

Didymo also needs high exposure to sunlight (not shaded). Score another point for the tailwaters vs the mountains.

The steadier, more regular flows of lake-fed and dam-controlled rivers suit didymo better than the variable flows of mountain streams. It also appears that periodic high flows (flooding) help scour the streambed and discourage didymo growth.

And last, but probably not least, the pH levels of the Smokies streams are generally too low to suit didymo. The streams in the Smokies range from 4.8 - 7.4 in pH, with the average at 6.3. According to the above referenced report, didymo does better with more alkaline water averaging around 7.7 pH.

What that all boils down to, at least to me, is that the tailwaters provide an ideal growing environment for the nasty bugger that is rock snot, but the majority of freestone streams in the mountains really aren't that threatened. At least not by didymo. We'll save the discussion of acidity, etc. for another day.

The other report I thought I had seen can be found here: http://www.biosecurity.govt.nz/files...ort-jun-07.pdf (Warning: another 1mb PDF file). According to what I gathered from a quick skimming, while didymo did lead to an overall increase in invertebrate drift biomass, the average size of the individual bugs was somewhat smaller. Also, there was insufficient data to conclusively prove anything one way or the other and more study will be required (of course).

Anyway, those reports should provide anyone who really wants to numb their brains several hours of light reading before bedtime. Enjoy.